(1) Technical Field
The subject invention relates to an improved lobe for use on a cam shaft assembly and a method for making a cam shaft assembly.
(2) Description of the Prior Art
Cam shaft assemblies are well known in the art. The assemblies require precision placement of the lobes to ensure proper operation of the engine in which they are used. Deviation of as little as one millionth of an inch can cause an assembly to be scrapped.
Currently, two main methods are used to create a shaft assembly. One way is cast the entire cam shaft. Once cast, the assembly must be extensively ground to the exact tolerances for proper use in the engine.
An alternative method is to fixedly attach preground lobes to a tubular shaft to create the cam shaft assembly. Such an assembly and method for making the same are shown in U.S. Pat. Nos. 4,693,138 granted Sept. 15, 1987 and 4,738,012 granted Apr. 19, 1988, each to Hughes et al. An apparatus used to make such an assembly is shown in U.S. Pat. No. 4,763,503 granted Aug. 16, 1988 to Hughes et al.
These prior art cam shaft assemblies and method for making the same are sometimes lacking in that the lobes can not be precisely located (within the required tolerances) angularly relative to the shaft while the lobes are being secured to the shaft. Therefore, once the lobes are secured on the shaft, they are required to be finally machined or ground in order to bring the cam shaft assembly to within the required tolerances.